Description Pseudouridine is a C-glycosyl pyrimidine that consists of uracil having a β-D-ribofuranosyl residue attached at position 5. The C-glycosyl isomer of the nucleoside uridine. It has a role as a fundamental metabolite. Pseudouridine is found in all species and in all classes of RNA except mRNA. It is formed by enzymes called pseudouridine synthases, which post-transcriptionally isomerize specific uridine residues in RNA.